1. Field of the Invention
The present invention relates to a system condensing infrared rays for the detection of a human body.
2. Description of the Related Arts
A conventional system for detecting a human body shown in FIGS. 12 and 13, by way of example, is disclosed in Japanese Laid-open Patent Publication No. Hei-1-227987. FIG. 12 is a block diagram, while FIG. 13 is a view explaining a manner detecting a position of the human body within a room.
In the figures, reference numerals 1A to 1C denote partial detection regions each having an elongated zone, reference numerals 3A to 3C designate condensers for gathering light rays emitted from the partial detection regions, reference numerals 4A to 4C indicate infrared detectors for selectively detecting infrared rays radiated from the human body, reference numeral 5 signifies a plurality of amplifiers for amplifying outputs from the infrared detectors 4A to 4C, and reference numeral 6 represents a plurality of binarizing apparatus for comparing the amplified signals with a reference value for binarization.
In the known human body detection system thus configured, the light rays condensed by the condensers 3A are directed through the partial detection region 1A defined as an elongated zone to the infrared detector 4A. The infrared detector 4A detects a variation in the infrared rays radiated from the human body with the aid of an optical filter, and transmits detection signals to tile associated amplifier 5. At that time, the infrared detector 4A selectively detects an infrared rays having a wavelength in the order of 10 micron which is a center wavelength of the infrared rays radiated from the human body.
The amplifier 5 receives the detection signals to amplify them to a predetermined level. This amplification factor depends on a distance between the system and the human body to be detected since light attenuates in proportion to the square of the distance. Thus amplified signals are binarized by a binarization apparatus 6 having a reference value equal to a signal level at the farthest distance within the partial detection region 1A, thereby judging "0" or "1" based on voltage levels of the signals.
When the human body exists within the partial detection region 1A of the condenser 3A in this way, a corresponding output of the binarization apparatus 6 is generated as a human body position signal. In the same manner, when the human body exists within the partial detection region 1B or 1C of the condenser 3B or 3C, the respective human body position signals are separately detected irrespective of the different amplification factor of the amplifier 5 and the different reference value of the binarization apparatus 6. As a result, with any movement of the human body across any one of the partial detection regions 1A to 1C as shown in FIG. 13, it can be detected which region includes the human body.
in the conventional human body detection system as described above, a plurality of infrared detectors 4A to 4C, amplifiers 5 and binarization apparatus 6 must be provided corresponding to the partial detection regions 1A to 1C, respectively, and hence the number of the constituent elements is increased, which disadvantageously results in a higher production cost and miniaturization difficulty.